Provided are an image processing apparatus and method of controlling same for detecting, in pixel units, an edge that exists prior to encoding, thereby protecting an edge that exists prior to encoding and reducing noise produced by encoding. To accomplish this, the image processing apparatus compares a threshold value generated from quantization information of each pixel when decoding is performed, and the absolute values of differences between a pixel of interest and pixel peripherals thereto, detects, in pixel units, an edge that existed prior to encoding, and corrects only noise produced by encoding.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An image processing apparatus comprising: a decoding unit that decodes encoded image data; a quantization error calculating unit that acquires quantization information, which relates to quantization when said decoding unit decodes the image data, and calculates pixel-by-pixel quantization error; an edge map generating unit that generates an edge map, which represents whether or not each pixel is an edge portion, using the decoded image data and the calculated quantization error; a determination unit that determines whether or not noise is included in a pixel of interest that is to be processed, using the generated edge map; and a correction unit that corrects the image data of a pixel of interest which has been determined to include noise by said determination unit; and wherein said edge map generating unit includes: an input unit that inputs the value of the pixel of interest and values of a plurality of peripheral pixels situated in the vicinity of the pixel of interest; a difference calculating unit that calculates difference absolute values between the pixel of interest and each of the peripheral pixels; a threshold value generating unit that generates a threshold value for every peripheral pixel from the quantization error, the threshold value indicating whether or not the pixel is an edge portion; a comparison unit that compares each calculated difference absolute value and each respective generated threshold value; a selecting unit that, if the difference absolute value is greater than the threshold value, selects this difference absolute value as an output value, and that, if the difference absolute value is equal to or less than the threshold value, selects a prescribed value as an output value; and an adding unit that adds the output values, which have been selected for every difference absolute value, as the value of the pixel of interest in the edge map.
2. The apparatus according to claim 1 , wherein if the edge map indicates that the value of the pixel of interest is not an edge portion and that the value of at least one peripheral pixel situated in the vicinity of the pixel of interest is an edge portion, said determination unit determines that the pixel of interest includes noise.
3. The apparatus according to claim 1 , wherein said threshold value generating unit generates the total of the quantization error of the pixel of interest and the quantization errors of peripheral pixels situated in the vicinity of the pixel of interest as the threshold value.
4. The apparatus according to claim 1 , wherein the encoded image data is data that has undergone block compressive encoding.
5. An image processing apparatus comprising: a decoding unit that decodes encoded image data; a quantization error calculating unit that acquires quantization information, which relates to quantization when said decoding unit decodes the image data, and calculates pixel-by-pixel quantization error; an edge map generating unit that generates an edge map, which represents whether or not each pixel is an edge portion, using the decoded image data and the calculated quantization error; a determination unit that determines whether or not noise is included in a pixel of interest that is to be processed, using the generated edge map; and a correction unit that corrects the image data of a pixel of interest which has been determined to include noise by said determination unit; and wherein said edge map generating unit includes: an input unit that inputs the value of the pixel of interest and values of a plurality of peripheral pixels situated in the vicinity of the pixel of interest; a difference calculating unit that calculates difference absolute values between the pixel of interest and each of the peripheral pixels; an adding unit that adds the calculated difference absolute values; a threshold value generating unit that generates a threshold value for every peripheral pixel from the quantization error, the threshold value indicating whether or not the pixel is an edge portion, and that outputs a total value of the generated threshold values; a comparison unit that compares a total value of the added difference absolute values and the total value of the generated threshold values, respectively; and a selecting unit that, if the difference absolute value is greater than the threshold value, selects this difference absolute value as the value of the pixel of interest in the edge map, and that, if the difference absolute value is equal to or less than the threshold value, selects a prescribed value as the value of the pixel of interest in the edge map.
6. A method of controlling an image processing apparatus comprising: a decoding step of decoding encoded image data; a quantization error calculating step of acquiring quantization information, which relates to quantization when the image data is decoded at said decoding step, and calculating pixel-by-pixel quantization error; an edge map generating step of generating an edge map, which represents whether or not each pixel is an edge portion, using the decoded image data and the calculated quantization error; a determination step of determining whether or not noise is included in a pixel of interest that is to be processed, using the generated edge map; and a correcting step of correcting the image data of a pixel of interest which has been determined to include noise at said determination step, wherein a processor carries out said decoding, quantization error calculating, edge map generating, determination and correcting steps, and wherein said edge map generating step includes: an input step of inputting the value of the pixel of interest and values of a plurality of peripheral pixels situated in the vicinity of the pixel of interest; a difference calculating step of calculation difference absolute values between the pixel of interest and each of the peripheral pixels; a threshold value generating step of generating unit a threshold value for every peripheral pixel from the quantization error, the threshold value indicating whether or not the pixel is an edge portion; a comparison step of comparing each calculated difference absolute value and each respective generated threshold value; a selecting step of, if the difference absolute value is greater than the threshold value, selecting this difference absolute value as an output value, and, if the difference absolute value is equal to or less than the threshold value, selecting a prescribed value as an output value; and an adding step of adding the output values, which have been selected for every difference absolute value, as the value of the pixel of interest in the edge map.
7. A non-transitory computer-readable medium storing a computer program for causing a computer to execute each step in the method of controlling the image processing apparatus according to claim 6 .
8. A method of controlling an image processing apparatus comprising: a decoding step of decoding encoded image data; a quantization error calculating step of acquiring quantization information, which relates to quantization when the image data is decoded at said decoding step, and calculating pixel-by-pixel quantization error; an edge map generating step of generating an edge map, which represents whether or not each pixel is an edge portion, using the decoded image data and the calculated quantization error; a determination step of determining whether or not noise is included in a pixel of interest that is to be processed, using the generated edge map; and a correcting step of correcting the image data of a pixel of interest which has been determined to include noise at said determination step, wherein a processor carries out said decoding, quantization error calculating, edge map generating, determination and correcting steps, and wherein said edge map generating step includes: an input step of inputting the value of the pixel of interest and values of a plurality of peripheral pixels situated in the vicinity of the pixel of interest; a difference calculating step of calculating that difference absolute values between the pixel of interest and each of the peripheral pixels; an adding step of adding the calculated difference absolute values; a threshold value generating step of generating a threshold value for every peripheral pixel from the quantization error, the threshold value indicating whether or not the pixel is an edge portion, and that outputs a total value of the generated threshold values; a comparison step of comparing a total value of the added difference absolute values and the total value of the generated threshold values, respectively; and a selecting step of, if the difference absolute value is greater than the threshold value, selecting this difference absolute value as the value of the pixel of interest in the edge map, and, if the difference absolute value is equal to or less than the threshold value, selecting a prescribed value as the value of the pixel of interest in the edge map.
9. A non-transitory computer-readable medium storing a computer program for causing a computer to execute each step in the method of controlling the image processing apparatus according to claim 8 .
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October 21, 2009
October 8, 2013
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